1. Field of the Invention
The present invention relates to a method of detecting a color level and a color phase on the basis of a color video signal and a color video signal detector for carrying out the method.
2. Description of the Related Art
In a television set for displaying images, a color level and a color phase of a color video signal are detected by extracting a blue primary color signal included in a color bar signal. As shown in (a) of FIG. 5, the color bar signal represents, for example, in order of luminance, a white bar, a yellow bar, a cyan bar, a green bar, a magenta bar, a red bar and a blue bar, and color signals representing those color bars are produced by mixing primary color signals, i.e., a green primary color signal, a red primary color signal and a blue primary color signal as shown in (b) of FIG. 5 by an additive color mixing method; that is, a white color bar is produced by mixing green, red and blue primary color signals, a yellow bar is produced by mixing green and red primary color signals, a cyan bar is produced by mixing green and blue primary color signals, and a magenta bar is produced by mixing red and blue primary color signals.
When the color bar signal is regulated correctly, the level of the blue primary color signal is the same at positions for the white, the cyan, the magenta and the blue bar of the color bar signal as shown in (b) of FIG. 5, and the blue primary color signal is given every other color bar when the color bars are arranged in order of luminance. In the aforesaid arrangement of the seven color bars or an arrangement of eight color bars including a black bar in addition to the seven color bars, it is common practice to provide the blue primary color signal, a gate signal which becomes active whenever the four color bars, i.e., the white, the cyan, the magenta and the blue bars, appear, and to assume that the respective widths of the color signals are the same. The levels of the blue primary color signal for the white, the cyan, the magenta and the blue bars are then extracted to detect the color level and the color phase of a color video signal.
However, since the gate signal is generated on an assumption that the widths of the color signals are the same and is not synchronized with the color bar signal, there is a possibility that there are times when the gate signal becomes active which are not synchronous with the blue primary color signal.
Since the seven-color bar signal and the eight-color bar signal are different from each other when the blue primary color signal is provided, the color level and the color phase of the color video signal cannot be detected by using the same gate signal, and the conventional color video signal detector needs to generate a plurality of gate signals and hence the color video signal detector has a comparatively large number of operations. It goes without saying that there still remains a problem in timing the gate signal even if a plurality of gate signals are provided.